No question is silly! This is a good one.
Ball is kind of a generic term which can be confusing. It usually refers to any yarn that is wound into a ball (round) or a cake (round and flat on top and bottom).
A hank of yarn is in a twist. If the yarn is in a hank you need to wind it somehow because its almost impossible use without it. . Some people do it by hand and some use a ball winder. A ball winder turns out little cakes of center pull balls. You can also pull from the outside if you prefer. Some yarns need to be used from the outside.
A skein is is the yarn that comes with the wrapper around the middle and can be used as center pull or outside pull. Wether you rewind is personal preference.
I don't have a ball winder (yet) so I wind my own center pull balls. Mine come out surprisingly close to a ball winder shape. I use the video on the bottom of this page.